The best & worst flammable trees & 7 or­ganic ways to fight weeds

Which trees in NZ are most (and least)
One of the most flammable is a fa­mous na­tive tree species, and it’s not manuka.

New re­search has shown some of the most flammable plants found in the NZ coun­try­side are gorse, eu­ca­lypts, and sur­pris­ingly to the sci­en­tists, rimu and sil­ver beech. That two wide­spread na­tive trees were sim­i­lar to highly flammable over­seas species was news to those tak­ing part in the joint Lin­coln Univer­sity and Univer­sity of Auck­land study.

Their work is the first ex­per­i­men­tal mea­sure­ment of the flamma­bil­ity of a large num­ber of plants found in NZ, and data gath­ered will be used to iden­tify fire-prone ecosys­tems and the best plants to use as 'green' fire­breaks to re­duce the spread of de­struc­tive wild­fires, likely to be more com­mon as a re­sult of cli­mate change.

Ex­ist­ing lists of suit­able non-flammable species in New Zealand are mostly based on ex­pert opin­ion, says Auck­land Univer­sity Pro­fes­sor Ge­orge Perry.

“Our re­sults pro­vide the first ex­per­i­men­tal ev­i­dence to sup­port cur­rent guide­lines on New Zealand plant flamma­bil­ity. This pro­vides rec­om­men­da­tions for coun­cils and fire man­agers on which na­tive New Zealand species to plant in green fire­breaks to re­duce fire spread.”

The team – which in­cluded All Black Sam White­lock, who was fin­ish­ing his Bach­e­lor of Sci­ence – placed shoots on a spe­cial ‘plant bar­beque’ made out of a 44 gal­lon drum cut in half with a grill on top. They lit sam­ples with a blow­torch and recorded how quickly they ig­nited, how hot they got, how long they burned for, and how much of the sam­ple burned.

Fu­ture ex­per­i­ments will in­clude a wider range of plants, and ul­ti­mately be con­ducted on plant com­mu­ni­ties in the field.

The sci­en­tists will also look at ‘mixed grill’ sit­u­a­tions where a highly flammable species like gorse is in­ter­spersed with a low flamma­bil­ity tree such as Co­prosma ro­busta (karamu) to see how fast or slow the com­bi­na­tion burns.

Dr Tim Cur­ran of Lin­coln Univer­sity demon­strat­ing the test­ing of tree flamma­bil­ity in a pur­pose-built burner.